I've read both the cognitive behavioral conceptualization of Hunter et al, the results of their clinical trial and also their book "Overcoming Depersonalization and Feelings of Unreality". In my opinion their approach is flawed and largely based on speculativ assumptions.
The clinical trial:
What they don't tell you in the abstract, but in the full text: In their trial they only achieved small effect sizes on measures of depersonalization post-treatment. Effect sizes on measures for depression and anxiety were higher, but lower than in many psychotherapy-trials for these symptoms. The only notable thing is "29% of participants no longer met criteria for DPD at the end of therapy", which might be a hint, that there is a subgroup, which received significant benefit, while the others did not. There was no control group, so it could also be placebo-effect.